If it's very urgent, then you shouldn't be relying on the forums. cPanel have said that you can log tickets directly with them for issues resulting from the mbox to maildir conversion, so you should do so.

Indeed. Except this thread contains no information from those posting as to what they've done to investigate and what their logs say. Neither do they say what cPanel's response is. So, in this case, it is not helpful and posting "me too" isn't constructive Logging a ticket with for this with cPanel is.